They are known for their massacre of Anne Hutchinson and her family during Kieft's War in 1643. In August 1643, a group of Siwanoy led by the sachemWampage massacred Hutchinson's household of 16 people near Split Rock, an ancient landmark. The only survivor was Hutchinson's nine-year-old daughter, Susanna, who may have been spared because of her red hair. The attack was in revenge for New Netherland governor Willem Kieft's February massacres of Wappinger refugees from Wecquaesgeek at Corlaer's Hook and Pavonia. Like thousands of Native Americans and numerous colonists, Hutchinson became caught up in the bloody reprisals which characterized the two year conflict. The Siwanoy attack killed Hutchinson, six of her children, and nine others.[2]

On June 27, 1654, Thomas Pell, a Connecticut physician, obtained title to a large amount of Siwanoy territory in New York through a treaty with a number of sachems, including Wampage. This included the Pelham Islands and parts of the mainland Bronx and coastal Westchester. New Netherland authorities did not recognize his title. They accused the New Englanders of continued encroachment upon Dutch territory. Pell's coup turned out to be decisive in New York history. A militia of his colonists from Minneford Island (present-day City Island) supported the English naval invasion force that conquered New Amsterdam in 1664.